This invention relates to steering columns, more specifically, it relates to the locking mechanism of a telescopic steering column.
Steering columns are normally both telescopic and tiltable, so that a user can adjust the position of a steering wheel by pivoting the steering column and or moving the steering wheel for and aft in the direction of said steering column.
Steering columns are often manufactured in small and customized series. Often, the steering column must be manufactured with a customized length and diameter, to suit the vehicle in which it is to be installed. For this reason, it is advantageous if as many of the components of the steering column as possible can be standardized, i.e. the same for all series.
Modern day vehicles, especially off-high way industrial vehicles, require the driver to control multiple various functions of the vehicle, such as for instance manoeuvring the bucket of a wheel-loader. Therefore, the space in the vicinity of the driver is limited; it is therefore advantageous if the steering column can be compact.
It is further advantageous for the locking mechanism to allow for quick and easy adjustment of the locking mechanism. The locking mechanism may need to be adjusted during assembly of the steering column to compensate for production deviations of the parts. The locking mechanism may also need to be adjusted when the steering column is installed in a vehicle, e.g. for the purpose of compensating for wear of the parts. In this instance, it is important that a mechanic is allowed easy access to the adjustment means.
It is previously known from the prior art a telescope lock for a steering column which lock includes a frictional plate disposed in a window of an outer jacket and in contact with an inner jacket. The frictional plate locks the jackets relative one another in the axial direction when said plate is subjected to a force which urges the frictional plate towards the axes of the jackets. This mechanism includes a pivotal lever which is pivoted by rotation of an actuation lever.
Previously known are also various types of cam mechanisms used in locking mechanism for telescopic steering columns.
To use a cam mechanism, i.e. two cam members with co-operating inclined surfaces, one of which is connected to a pivotal lever such that when the lever is pivoted, the effective width of the cam mechanism is increases, in order to lock a telescopic function of a steering column as such is known. Patents that show cam mechanisms includes for example U.S. Pat. No. 7,010,966, US 2006/0207378, U.S. Pat. No. 7,413,222, US 2005/0217407, U.S. Pat. No. 5,921,577 and U.S. Pat. No. 7,516,985.
These prior art references discloses a telescopic lock which includes a bracket comprising two sidearm's which are disposed on either side of a jacket. A bolt connects the two sidearms and the cam mechanism is disposed on this bolt. When a cam mechanism is activated, i.e. widened, it locks the jacket by decreasing the distance between the two sidearms.
A telescopic steering column with such configuration suffers from the disadvantage that the sidearms, and therefore, the locking mechanism, will protrude from the steering column and into the driver's compartment of the vehicle.
Another prior art reference, JP100 53 144 A, discloses a telescope lock in which two clamps, bracket parts, are disposed around an outer jacket, a frictional plate disposed in a window of the outer jacket and in contact with an inner jacket, a locking mechanism connected to a pivotal lever. The locking mechanism includes a boss disposed on and protruding from said outer jacket, the boss is internally threaded, a threaded rock bolt is disposed in said boss and connected to said pivotal lever. When the pivotal lever is pivoted, the rock bolt is rotated in the boss and consequently, it pushes the frictional plate into connection with the inner jacket according to its FIG. 2.
Another prior art reference, U.S. Pat. No. 7,516,985, discloses a locking mechanism for the telescopic movement between two jackets of a steering column. Incidentally, the same locking mechanism is used to lock the pivotal movement of the jackets as well. The locking mechanism comprises a first bracket which is attached to the outer jacket, the first bracket includes two sidewalls which includes two longitudinal slots which are parallel to the axis of the outer jacket, but disposed at a distance from the circumference from the jacket, such to allow a bolt to go through both of them. The locking mechanism further includes a second bracket which comprises two sidewalls which are disposed outside and parallel to the two side walls of the first bracket, a lock bolt is disposed through windows in the two side walls of the second bracket and said longitudinal slots. On a first side, the bolt is non-rotationally connected to a pivotal lever, the proximal end of the lever constitutes a first earn member which includes a cam surface which is circumferentially distributed around the lock bolt. Rotationally disposed on the lock bolt is a second cam member. On a second side of the bolt, the bolt is threaded and is intended to receive a nut.
In operation, the locking mechanism operates such that when the operational lever is turned, the cam members will effectively increase or decrease their effective width and thus compress or release the second bracket's side walls, respectively, thus clamping or unclamping the first bracket.